Field
The present invention relates to control of an environmental heater in an image forming apparatus.
Description of the Related Art
In an image forming apparatus including an electrophotographic process, a defective image is sometimes created due to condensation caused by an environmental change such as a decrease in temperature during night hours or early morning hours in a certain season in a certain region or the rapid increase in room temperature caused by air conditioning after the start of a business day in an office environment.
In the field, installing an environmental heater in an image forming apparatus by a serviceman based on the serviceman's determination or in response to a user's request, can result in a configuration where condensation is prevented. The environmental heater can be manually switched on and off. Such an environmental heater can be an AC heater that uses an AC power supply (see Japanese Patent Laid-Open No. 2009-216827).
In recent years, there have been demands for the further stabilization of image quality and for further increase in the lifetime of image forming apparatuses. In order to help meet these demands, further stabilization of a temperature around a photosensitive drum in an electrophotographic process has been proposed.
While the environmental heater disclosed in Japanese Patent Laid-Open No. 2009-216827 can respond to variations in rated values of commercial AC power supplies in various sales areas, it cannot respond to variations in voltages of commercial AC power supplies. Because of the variations in voltages of commercial AC power supplies, the amount of heat generation of an AC heater varies, and it is difficult to suppress an associated temperature ripple. In order to address this, a method has been proposed that employs, as an environmental heater, a DC heater using a DC power supply produced from a commercial AC power supply instead of an AC heater.
The operation of an environmental heater in a power save mode in which an image forming apparatus does not operate is particularly effective. However, in a case where a plurality of DC heaters are required to be located as environmental heaters and are connected to a power supply for a control circuit that operates in the power save mode, the power consumption of a control unit increases in a mode (for example, a standby mode or an image forming mode) other than the power save mode. It is therefore necessary to employ a high-power power supply capable of outputting both the increase in the power consumption of the control unit and the total amount of power consumption of the DC heaters. This leads to the increase in the power consumption in the power save mode.